1. Field of the Invention
The invention relates to functionalized propylene polymer compositions and, more specifically, compositions comprised of two different propylene polymers, both of which contain carboxylic acid or carboxylic acid derivative functionality. The mixed functionalized propylene polymer products of the invention are utilized as compatibilizing/coupling agents to facilitate incorporation of fillers and/or non-compatible resins into polypropylene base resins and provide composites having improved properties.
2. Description of the Prior Art
Multi-phase polypropylene (PP) composites are widely utilized for a variety of applications. For example, PP is commonly combined with non-compatible polymers, such as polyamides and ethylene-vinyl alcohol (EVOH) copolymers, to provide compositions suitable for films, coatings and moldings having improved barrier and physical properties. Similarly, PP and engineering thermoplastics are often blended to produce compositions and molded articles having improved mechanical properties. In other instances, various filler materials, such as mineral fillers, glass fibers and cellulosic fibers, are incorporated into PP to provide reinforced compositions having a desired balance of stiffness, impact strength, etc. For certain other applications, hydrated inorganic fillers are included in PP compositions to reduce flammability. In still other instances PP is combined with both a non-compatible polymer and filler material, e.g., nylons and glass fibers, to produce reinforced polymer composites.
It is accepted practice to include one or more functionalized compounds, commonly referred to as coupling agents and/or compatibilizing agents, to facilitate dispersion and/or bonding of the non-compatible polymers and/or filler materials with the non-polar PP polymer. It is generally believed that the functionalized compounds interact at the interface of the components to enhance compatibility of the additive component(s) and thus increase their desirable affect and provide composites having improved properties. Functionalized compounds commonly employed as coupling/compatibilizing agents include olefin polymers grafted with ethyleneically unsaturated carboxylic acids, hydrogenated vinyl aromatic/conjugated diene block copolymers grafted with ethylenically unsaturated carboxylic acids, olefin/acrylic ester/ethylenically unsaturated carboxylic acid terpolymers and olefin/acrylic ester/glycidyl acrylate terpolymers.
Functionalized propylene-ethylene copolymers have been disclosed as coupling/compatibilizing agents for wood fiber-filled PP compositions in published International Publication No. WO 02/059196 A1. The compositions contain 40–70 weight percent (wt. %) crystalline propylene polymer of specified tacticity and molecular weight distribution, 20–60 wt. % wood fiber and 0.3–12 wt. % functionalized olefin polymer. Whereas functionalized homopolymers of propylene are preferred, copolymers of propylene with another α-olefin, such as ethylene, are also mentioned.
Fiber-reinforced polymer composites containing 30–90 wt. % polyamide, 5–50 wt. % glass fibers and 10–70 wt. % polyolefin, of which a portion can be an unsaturated carboxylic acid-modified polyolefin, are disclosed in U.S. Pat. No. 4,990,550. The reference indicates that the polyolefins modified with unsaturated carboxylic acids or their derivatives are not limited to homopolymers of α-olefins but include copolymers of different α-olefins. Random and block copolymers of propylene and other α-olefins, most notably ethylene, wherein the propylene content is 50 mol % or more and, more preferably, 80 mol % or more are specifically mentioned.
Glass-filled polyolefin composites comprising propylene polymer of specified tacticity and MWD, ethylene/C4-6 α-olefin plastomer and functionalized olefin polymer are disclosed in International Publication No. WO 97/33941. Grafted homopolymers and copolymers of propylene are disclosed. The reference also suggests that all or a portion of the impact modifier can be functionalized.
U.S. Pat. No. 5,514,745 discloses glass fiber reinforced molding compositions consisting of a PP resin and a long glass fiber reinforced PP masterbatch wherein glass fibers are surface-finished with a finishing agent containing a coupling agent which is impregnated with a modified PP having functionality capable of reacting with the coupling agent. Carboxylic acid and anhydride-modified PP resins are disclosed as useful modified PPs.
U.S. Pat. No. 5,324,755 discloses the use of polyethylene, polypropylene and copolymers of ethylene and propylene chemically modified with ethylenically unsaturated carboxylic acid or derivatives as coupling agents in compositions with propylene polymers grafted with styrenic monomer, glass fiber and, optionally, one or more rubber polymer components.
Published U.S. patent application US 2001/0033924 A1 discloses nanocomposite concentrate compositions comprised of a layered silicate material and a polyolefin matrix polymer. The polyolefin matrix polymer is comprised of maleic anhydride-modified polyolefin and unmodified polyolefin. The layered silicate is intercalated with the matrix polymer which can be in the form of a polymer or oligomer capable of polymerization to form the polymer. The reference indicates that impact copolymers containing ethylene-propylene rubber can be used as the matrix polymer and polymer intercalate for the invention.
Functionalized propylene-ethylene impact copolymers which are reactor-made intimate mixtures of propylene homopolymer and propylene-ethylene copolymer produced in gas-phase, stirred-bed, multi-stage polymerization processes are disclosed to be useful compatibilizing/coupling agents for propylene polymer composites in copending application Ser. No. 10/816,389.
Polyamide/olefin polymer blend compositions utilizing a plurality of compatibilizing agents are disclosed in U.S. Pat. No. 5,317,059. A first compatibilizing agent which is a terpolymer of an α-olefin, an acrylic ester and an alpha, beta-olefinically unsaturated dicarboxylic acid or glycidyl acrylate and auxiliary compatibilizing agent are employed. Ethylene-propylene elastomers grafted with maleic anhydride are mentioned as a type of auxiliary compatibilizing agent which can be used for the invention.
There is a continuing need for new functionalized compatibilizing/coupling agents suitable for use in the formulation of propylene polymer composites. It is particularly desirable when composites obtained using these functionalized materials have improved physical properties. These and other objectives are achieved with the mixed functionalized propylene polymer compositions of the invention.